<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    @keyframes ani {
      0%{
        transform: rotate(45deg);
      }
      100%{
        transform: rotate(-45deg);
      }
    }
    .box{
      width: 20px;
      height: 200px;
      background-color: rgb(201, 92, 20);
      margin: 100px auto;
      transform-origin: center bottom;
      animation: ani 50ms infinite alternate linear;
    }
  </style>
</head>
<body>
  <div class="box"></div>
</body>
</html>